#include <iostream>
using namespace std;

const double PI = 3.1415926;

class Point{
    private :
        double x, y;
    public :
        Point(double i, double j)
        {
             x = i;
             y = j;
        }
    virtual double area(){return 0;}
    
};

class Circle : public Point{
    private :
        double radius;
    public :
        Circle(double a,double b, double r):Point(a, b)
        {
            radius = r;
        }
        double area(){
            return PI * radius * radius;
        }
};

void display(Point *p)
{
    cout << p -> area() << endl;
}

void display(Point &a){
    cout << a.area() << endl;
}

int main()
{
    Point a(1.5, 6.7);
    Circle c(1.5, 6.7, 2.5);
    Point *p = &c;
    Point &rc = c;
    display(a);
    display(p);
    display(rc);

    return 0;
}

